Inhibition of nitrogen mustard after-effect in F--cells by the factor produced by E. coli K-12 fertile strains

1. Hfr, F+ and RTF strains of E. coli produce an extracellular inhibitor of nitrogen mustard after-effect (NMAE) in NM-treated F--cells. 2. The NMAE inhibiting factor is a non-dialyzable protein. 3. The NMAE inhibiting factor is inactive in F-rec- and F-uvr--cells treated with NM.